Effects of silicon tetrachloride concentration on nanocrystalline silicon films growth

The effects of the silicon tetrachloride (SiCl₄) concentration on the growth of the nanocrystalline silicon film using SiCl₄/hydrogen (H₂) reactants are investigated here. An almost twice enhancement of the deposition rate of the silicon film, while still maintaining the film with a high crystal fraction at a level of 96%, is achieved by increasing the SiCl₄ concentration from 17 to 26% at a substrate temperature of 270 °C. The similar trends of the crystal fraction and deposition rate with the SiCl₄ concentration are also observed from those films deposited at 180 °C. The morphologies of the nanocrystalline silicon films with a thickness of 460 nm which deposited at 270 °C from various SiCl₄ concentrations are similar whereas they are drastically different as the film thickness increases to 2.6 μm. The roles of the SiCl₄ concentration, which relates to Cl radical and H radical concentrations in gas phase, in the growth behaviors of the nanocrystalline silicon films are discussed.